Neisseria meningitidis is a Gram-negative encapsulated bacterium which colonises the upper respiratory tract of approximately 10% of human population. Approximately once in every 10,000 colonised people (or once in 100,000 population) the bacterium enters the blood stream where it multiplies and causes sepsis. From the blood stream the bacterium can cross the blood-brain barrier and cause meningitis. Both diseases are devastating and can kill 5-15% of affected children and young adults within hours, despite the availability of effective antibiotics. Up to 25% of those who survive are left with permanent sequelae.
Prevention of disease has been partially accomplished by vaccination. Immunisation was made possible in 1969 when it was discovered that protection from disease correlates with the presence of serum antibodies able to induce complement-mediated killing of bacteria, and that purified capsular polysaccharide was able to induce these antibodies. Although polysaccharide and conjugate vaccines are available against serogroups A, C, W135 and Y, this approach cannot be applied to serogroup B because the capsular polysaccharide is a polymer of polysialic acid, which is a self antigen in humans. To develop a vaccine against serogroup B, surface-exposed proteins contained in outer membrane vesicles (OMVs) have been used. These vaccines elicit serum bactericidal antibody responses and protect against disease, but they fail to induce cross-strain protection [1].
The complete genome sequence of serogroup B N. meningitidis has been published [2] and has been subjected to analysis in order to identify vaccine antigens [3]. The complete genome sequence of serogroup A N. meningitidis is also known [4], and the complete genome sequence of Neisseria gonorrhoeae strain FA1090 is available [5]. References 6 to 9 disclose proteins from Neisseria meningitidis and Neisseria gonorrhoeae, and approaches to expression of these proteins are disclosed in references 10 to 12.
It is an object of the invention to provide further and improved compositions for providing immunity against meningococcal disease and/or infection, particularly for serogroup B.